Roy Riascos

Neuroimaging in drug and substance abuse part II: Opioids and solvents

The central nervous system is one of the primary targets for the detrimental effects of drugs of abuse. Diagnostic imaging, especially MRI, plays an important role in the detection of complications associated with drug abuse. We present the imaging findings associated with the abuse of opioids and other morphine derivatives, as well, as solvents. Of the morphine derivatives, heroin is the most commonly abused. Several CNS pathologic effects have been described in association with its abuse. These include neurovascular complications such as microvascular ischemic changes or ischemic stroke. A rare form of leukoencephalopathy has been described in those abusers who inhale heroin vapors. Other neurologic complications include atrophy and various infectious processes. Solvent inhalation is a common practice among adolescents and young adults secondary to its ease of access and low cost. The most important component of industrial solvents is toluene. Complications of toluene abuse may be either acute, showing no neuroradiological changes, or chronic, characterized by cerebral and cerebellar demyelination as well as atrophy.

Optic disc edema in an astronaut after repeat long-duration space flight

Background: A number of ophthalmic findings including optic disc edema, globe flattening, and choroidal folds have been observed in several astronauts after long-duration space flights. The authors report the first astronaut with previously documented postflight ophthalmic abnormalities who developed new pathological changes after a repeat long-duration mission. Methods: A case study of an astronaut with 2 long-duration (6 months) exposures to microgravity. Before and after his first long-duration space flight, he underwent complete eye examination, including fundus photography. Before and after his second flight, 9 years later, he underwent fundus photography, optical coherence tomography, ocular ultrasonography, and brain magnetic resonance imaging, as well as in-flight fundus photography and ultrasound. Results: After his first long-duration mission, the astronaut was documented to have eye findings limited to unilateral choroidal folds and a single cotton wool spot. During a subsequent 6-month mission, he developed more widespread choroidal folds and new onset of optic disc edema in the same eye. Conclusion: Microgravity-induced anatomical changes that occurred during the first mission may have set the stage for recurrent or additional changes when the astronaut was subjected to physiological stress of repeat space flight.

Nonvascular, Nontrau-Matic mediastinal emer-gencies in adults: A Comprehensive Review of Imaging Findings

Given their high frequency, mediastinal emergencies are often perceived as being a result of external trauma or vascular conditions. However, there is a group of nonvascular, nontraumatic mediastinal emergencies that are less common in clinical practice, are less recognized, and that represent an important source of morbidity and mortality in patients. Nonvascular, nontraumatic mediastinal emergencies have several causes and result from different pathophysiologic mechanisms including infection, internal trauma, malignancy, and postoperative complications, and some may be idiopathic. Some conditions that lead to nonvascular, nontraumatic mediastinal emergencies include acute mediastinitis; esophageal emergencies such as intramural hematoma of the esophagus, Boerhaave syndrome, and acquired esophagorespiratory fistulas; spontaneous mediastinal hematoma; tension pneumomediastinum; and tension pneumopericardium. Although clinical findings of nonvascular, nontraumatic mediastinal emergencies may be nonspecific, imaging findings are often definitive. Awareness of various nonvascular, nontraumatic mediastinal emergencies and their clinical manifestations and imaging findings is crucial for making an accurate and timely diagnosis to facilitate appropriate patient management.

Diffusion tensor imaging of the human cerebellar pathways and their interplay with cerebral macrostructure

Cerebellar white matter (WM) connections to the central nervous system are classified functionally into the Spinocerebellar (SC), vestibulocerebellar (VC), and cerebrocerebellar subdivisions. The SC pathways project from spinal cord to cerebellum, whereas the VC pathways project from vestibular organs of the inner ear. Cerebrocerebellar connections are composed of feed forward and feedback connections between cerebrum and cerebellum including the cortico-ponto-cerebellar (CPC) pathways being of cortical origin and the dentate-rubro-thalamo-cortical (DRTC) pathway being of cerebellar origin. In this study we systematically quantified the whole cerebellar system connections using diffusion tensor magnetic resonance imaging (DT-MRI). Ten right-handed healthy subjects (7 males and 3 females, age range 20–51 years) were studied. DT-MRI data were acquired with a voxel size = 2 mm × 2 mm × 2 mm at a 3.0 Tesla clinical MRI scanner. The DT-MRI data were prepared and analyzed using anatomically-guided deterministic tractography methods to reconstruct the SC, DRTC, fronto-ponto-cerebellar (FPC), parieto-ponto-cerebellar (PPC), temporo-ponto-cerebellar (TPC) and occipito-ponto-cerebellar (OPC). The DTI-attributes or the cerebellar tracts along with their cortical representation (Brodmann areas) were presented in standard Montréal Neurological Institute space. All cerebellar tract volumes were quantified and correlated with volumes of cerebral cortical, subcortical gray matter (GM), cerebral WM and cerebellar GM, and cerebellar WM. On our healthy cohort, the ratio of total cerebellar GM-to-WM was ~3.29 ± 0.24, whereas the ratio of cerebral GM-to-WM was approximately 1.10 ± 0.11. The sum of all cerebellar tract volumes is ~25.8 ± 7.3 mL, or a percentage of 1.6 ± 0.45 of the total intracranial volume (ICV).

Fatal methadone intoxication in a child

Methadone is an opiate used as part of the treatment for heroin abuse; it can be ingested orally. We present the lethal outcome of a 22-month-old child intoxicated after methadone ingestion.

The neuroimaging of Leigh syndrome: case series and review of the literature

Leigh syndrome by definition is (1) a neurodegenerative disease with variable symptoms, (2) caused by mitochondrial dysfunction from a hereditary genetic defect and (3) accompanied by bilateral central nervous system lesions. A genetic etiology is confirmed in approximately 50% of patients, with more than 60 identified mutations in the nuclear and mitochondrial genomes. Here we review the clinical features and imaging studies of Leigh syndrome and describe the neuroimaging findings in a cohort of 17 children with genetically confirmed Leigh syndrome. MR findings include lesions in the brainstem in 9 children (53%), basal ganglia in 13 (76%), thalami in 4 (24%) and dentate nuclei in 2 (12%), and global atrophy in 2 (12%). The brainstem lesions were most frequent in the midbrain and medulla oblongata. With follow-up an increased number of lesions from baseline was observed in 7 of 13 children, evolution of the initial lesion was seen in 6, and complete regression of the lesions was seen in 3. No cerebral white matter lesions were found in any of the 17 children. In concordance with the literature, we found that Leigh syndrome follows a similar pattern of bilateral, symmetrical basal ganglia or brainstem changes. Lesions in Leigh syndrome evolve over time and a lack of visible lesions does not exclude the diagnosis. Reversibility of lesions is seen in some patients, making the continued search for treatment and prevention a priority for clinicians and researchers.

Cardiovascular complications of cocaine: Imaging findings

Cocaine is the second most commonly abused illicit drug in the US and the most common one involved in emergency department visits, the majority of which are related to the cardiovascular system. Cardiovascular complications related with cocaine abuse include myocardial ischemia and infarction, myocarditis, hypertrophic cardiomyopathy, dilated cardiomyopathy, aortic dissection, thrombosis, stroke and cerebral hemorrhage, and different forms of visceral ischemia, among others. In an era where cocaine use has reached epidemic proportions, it is necessary for the radiologist to understand the pathophysiology, clinical presentation, and imaging characteristics of its cardiovascular complications.

Neuroimaging in drug and substance abuse part I: Cocaine, cannabis, and ecstasy

Multiple neurological complications of cocaine abuse have been described including both ischemic and hemorrhagic cerebrovascular events, atrophy in the case of chronic abuse, and an increase in incidence of congenital malformations in the setting of maternal use. The abuse of cannabis may cause a number of neurovascular changes that, in turn, may result in ischemic events, however, a direct connection between these has not been fully established. The use of MDMA (ecstasy), a popular recreational drug, has been related to ischemic and hemorrhagic cerebrovascular events, as well as atrophy. Neuroimaging studies are vital in the assessment of the extent of neurologic damage in these patients.

Mapping the trajectory of the stria terminalis of the human limbic system using high spatial resolution diffusion tensor tractography

The human limbic system is composed of gray and white matter structures which have been known to have a role in core processes such as motivation, memory, emotion, social behavior, self-awareness as well as certain primitive instincts. Multiple functional studies investigated some of these brain tasks in human brain limbic system. However, the underlying fine fiber pathways of the limbic system including the trajectory of the stria terminalis have not been delineated separately by prior diffusion weighted imaging. The ability to trace the underlying fiber anatomy noninvasively using diffusion tensor tractography (DTT) would be helpful to study the neurophysiology of these tracts in different functions in future functional studies. Few studies have focused on the stria terminalis using diffusion tensor tractography. Yet, the trajectory of the stria terminalis and some fine subtrajectories of the fornix have not been elucidated by prior DTT studies. We decided to further investigate these fine neuronal trajectory using tractography and high spatial resolution diffusion tensor imaging on 3T. Fifteen healthy right-handed men (age range 24-37 years) were studied. We delineated the detailed trajectories of the stria terminalis and fornix bilaterally in fifteen normal adult human brains. Using a high resolution DTT technique, we demonstrate for the first time, the trajectory of stria terminalis as well as detailed precommissural and postcommissural connectivity of the forniceal columns.

Comprehensive Review of the Anatomy, Function, and Imaging of the Popliteus and Associated Pathologic Conditions

The popliteus is a relatively small but unique muscle of the knee. It is a component of the posterolateral corner of the knee and acts as a major stabilizer of the posterolateral knee. It is important to be aware of the normal magnetic resonance (MR) imaging appearance of the popliteus musculotendinous complex and its relation to other structures of the posterolateral corner for accurate diagnosis. It is also important to be aware of the pitfalls in imaging of the popliteus. Dysfunction of the popliteus is often underappreciated and is usually secondary to direct or indirect trauma. Injuries of the popliteus can be classified as first-, second-, or third-degree strains. Injuries of the popliteus are often associated with other posterolateral corner injuries. Pathologic conditions of the popliteus may be a clue to other injuries in the knee. The site and pattern of popliteus tear can be helpful to the orthopedic surgeon in deciding whether repair is warranted and determining the approach to surgery and has prognostic implications. Undiagnosed popliteus injuries can lead to poor functional results after knee reconstructive surgery. Inflammatory pathologic conditions of the popliteus may cause knee pain and can be diagnosed with MR imaging. The popliteus is an important component of the posterolateral corner that needs closer attention for optimal diagnosis and patient care.